Post by thread:[ot]: IR paper detector for a shredder

my shredder jammed and I discovered that the paper detector had been mangled and broke from its mount. This detector seems to be two clear led's fixed in a mount pointing down form above the paper slot at about a 45 degree angle, like a 'V' Question is, how does this thing work? It looks to me like two clear led's, how does it detect anything? Thanks... one of the led's is broken and I was wondering if I could just replace it, and have the thing work... I don't see how it detects anything. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spam_OUTlistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

I think that you will find that one is and LED and the other is an opto-receiver. The light from the LED (could be infra-red) reflects off the paper to cause the opto-receiver to conduct operating a relay, triac and turning on the motor. With no paper there is not sufficient reflected light so motor is switched off. Regards Chris {Quote hidden}> my shredder jammed and I discovered that the paper detector > had been mangled and broke from its mount. > > This detector seems to be two clear led's fixed in a mount > pointing down form above the paper slot at about a 45 degree > angle, like a 'V' > > Question is, how does this thing work? It looks to me like two > clear led's, how does it detect anything? > > > Thanks... > > one of the led's is broken and I was wondering if I could just > replace it, and have the thing work... > > I don't see how it detects anything. > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body > > > -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam.....mitvma.mit.edu

Most likely one of the items is really a phototransistor. These often come in packages that are exactly like LED's. The other is most likely an IR LED. You could probably distinguish them out of circuit by placing 5 v through 2000 ohms on the terminals - With the LED, with one polarity you will drop about 1.5 volts across the LED. If it is IR, you won't be able to see it lit up. Reverse biased it will be an open circuit. With the phototransistor, you will have a much smaller voltage drop if it is exposed to any light. In dark, it will be an open circuit. Reverse biased it will be an open circuit. You could probably replace these, once you figure out which is which, with any IR-LED and phototransistor pair say from Radio Shark. At any rate, it is worthwhile hacking them, because LED/phototransistor detectors are very common, and useful to understand. Good Luck! --Lawrence Lile {Original Message removed}

One of the LEDs will be an emitter, the other a sensor. Regards Ben To: EraseMEPICLISTspam_OUTTakeThisOuTMITVMA.MIT.EDU cc: From: rad0 <rden25spam_OUTMINDSPRING.COM> Subject: [ot]: IR paper detector for a shredder Question is, how does this thing work? It looks to me like two clear led's, how does it detect anything? ******************************************************************************* Important. This E-mail is intended for the above named person and may be confidential and/or legally privileged. If this has come to you in error you must take no action based on it, nor must you copy or show it to anyone; please inform the sender immediately. ******************************************************************************* -- http://www.piclist.com hint: To leave the PICList @spam@piclist-unsubscribe-requestKILLspammitvma.mit.edu

Hi, Iam guessing one will be an infra-red emitter and the other a detector. This sensor simply relies on the IR beam being reflected back into the detector by the sheet of paper, also these usually have an operating range of about 10mm (just guessing here) because of the 45Deg angle. I've seen ready made detector like these from most suppliers. Also if you fit a new one you may find you have to adjust a trim pot somewhere as these usually need calibrating as paper colour etc can affect performance, at least on the scanners and jukebox's I work on this needs to be done. cheers, Russ. {Original Message removed}

Probably one is an LED and the other a phototransistor. -Bob On Mon, 12 Mar 2001, rad0 wrote: > my shredder jammed and I discovered that the paper detector > had been mangled and broke from its mount. > > This detector seems to be two clear led's fixed in a mount > pointing down form above the paper slot at about a 45 degree > angle, like a 'V' -- http://www.piclist.com hint: To leave the PICList KILLspampiclist-unsubscribe-requestKILLspammitvma.mit.edu

> my shredder jammed and I discovered that the paper detector > had been mangled and broke from its mount. > > This detector seems to be two clear led's fixed in a mount > pointing down form above the paper slot at about a 45 degree > angle, like a 'V' > > Question is, how does this thing work? It looks to me like two > clear led's, how does it detect anything? My guess is that it isn't two LEDs but instead one IR LED and one IR phototransitor. The reflection difference between paper and no paper is what it detects. These should be pretty standard parts, hardest part in you're case is figuring out whether the LED or the phototransistor is damaged. TTYL -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

thanks very much, they look identical, how do you tell one from the other?? ----- Original Message ----- From: "Alan B. Pearce" <spamBeGoneA.B.PearcespamBeGoneRL.AC.UK> To: <TakeThisOuTPICLISTEraseMEspam_OUTMITVMA.MIT.EDU> Sent: Monday, March 12, 2001 3:26 AM Subject: Re: [ot]: IR paper detector for a shredder > it will not be two LEDs, but rather an LED and a detector diode. I would try > replacing it with a standard opto interrupter type unit, which it may well be > anyway. > > -- > http://www.piclist.com hint: To leave the PICList > RemoveMEpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu > > -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestEraseME.....mitvma.mit.edu

>they look identical, how do you tell one from the other?? There is normally an indicator on the case to indicate + and - for the LED, and possibly E and C for the transistor. These markings are often moulded into the case rather than printed on. -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestmitvma.mit.edu

On Mon, 12 Mar 2001 10:25:34 -0600, you wrote: >my shredder jammed and I discovered that the paper detector >had been mangled and broke from its mount. > >This detector seems to be two clear led's fixed in a mount >pointing down form above the paper slot at about a 45 degree >angle, like a 'V' > >Question is, how does this thing work? It looks to me like two >clear led's, how does it detect anything? One of them is not a LED - it's either a photodiode or phototransistor in a LED style package. -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestEraseMEEraseMEmitvma.mit.edu

> >they look identical, how do you tell one from the other?? > > There is normally an indicator on the case to indicate + and - > for the LED, and possibly E and C for the transistor. These > markings are often moulded into the case rather than printed > on I've had the odd one with no markings, in which case it's trial and error. You can find which is which (and the polarity of the emitter, a diode) with an ohmmeter. For 5V operation put a 220R resistor in series with the emitter and ground the other side. The polarity of the detector may not be obvious. Put a 10k resistor in series with it and ground the other side. 5V goes to the other end of the 10k resistor. If you got it right (50/50 chance), you'll see the voltage at the 10k/detector pin junction dip when you point the opto at a piece of white paper. If nothing happens reverse the connections to the detector -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestspam_OUTKILLspammitvma.mit.edu

Hello, I had the unfortunate task of repairing paper shredders for a number of years. What you describe is an infrared detector pair. One led is an infrared emitter and the other is a photo transistor detector. The paper going through the machine provides a reflective surface (white paper is about 80% reflective) and the infrared photo transistor detects the reflected infrared that is emitted by the led. You should be able to use any readily available infrared led/photo transistor, assuming it will fit. The infrared led may be fed directly from the power supply (with limiting resistor) assuming it is not "chopped". Jim Albers On Mon, 12 Mar 2001 10:25:34 -0600 rad0 <RemoveMErden25TakeThisOuTspamMINDSPRING.COM> writes: {Quote hidden}> my shredder jammed and I discovered that the paper detector > had been mangled and broke from its mount. > > This detector seems to be two clear led's fixed in a mount > pointing down form above the paper slot at about a 45 degree > angle, like a 'V' > > Question is, how does this thing work? It looks to me like two > clear led's, how does it detect anything? > > > Thanks... > > one of the led's is broken and I was wondering if I could just > replace it, and have the thing work... > > I don't see how it detects anything. > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email EraseMElistservspamspamBeGonemitvma.mit.edu with SET PICList DIGEST in the body > > -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestKILLspammitvma.mit.edu

Thanks Jim, I'm going to machine a little block of aluminium and drill some holes at a 45 degree angle and put some silicon into the hole to hold the led/pair this ought to fix it one lead on one led is broken and I should be able to solder it back together, the plastic mounting case was destroyed... Thanks all... {Original Message removed}